Pearlescent Metallic Effect Paper Material With High Lightfastness And Related Manufacturing Method

ABSTRACT

The paper material comprises a base support, made up of a mixture of cellulose fibres containing at least one polymeric substance, which is adapted to give the mixture of fibres mechanical strength, and an inorganic filler, said base support having at least one surface treated with at least one surface adhesive and at least one coating applied on said treated surface, the coating comprising at least pearlescent pigments of high lightfastness.

The present invention refers to a paper material (paper/card) and to therelative manufacturing method.

In the paper sector, there is a constant search for new types of paperhaving particular characteristics and finishes, especially papersdesigned for packing, packaging, realizing illustrative material,quality printing, etcetera.

However, it is not uncommon that the achievement of special effects isdetrimental to other characteristics of the paper, such as printability.

A technical task of the present invention is to provide a paper materialthat has a different optical effect from conventional paper materials,while also being printable with high printing quality.

This technical task is solved by a paper material comprising a basesupport, made up of a mixture of cellulose fibres containing at leastone polymeric substance, which is adapted to give the mixture of fibresmechanical strength, and an inorganic filler, said base support havingat least one surface treated with at least one surface adhesive and atleast one coating applied on said treated surface, characterized in thatsaid coating comprises at least pearlescent pigments of highlightfastness.

The present invention also discloses a method for manufacturing thepaper material, comprising the steps of:

preparing an aqueous pulp of cellulose fibres, containing at least onepolymeric substance adapted to give the mixture of fibres mechanicalstrength, and an inorganic filler;

removing water from the pulp so as to form a base support of the papermaterial;

treating at least one surface of the base support with at least onesurface adhesive;

performing a smoothing process on the treated surface of the basesupport;

applying a coating comprising at least pearlescent pigments of highlightfastness to the smoothed treated surface.

In a preferred embodiment the pearlescent pigments are borosilicates oraluminosilicates and in particular micas.

In a preferred embodiment the pearlescent pigments are transparentborosilicates or aluminosilicates coated with metal oxides such as ironoxides, titanium oxides or tin oxides.

In a preferred embodiment the pearlescent pigments are of variouscolours, particle sizes and shapes.

In a preferred embodiment the coating comprises one or more binderpolymers and/or waxes, in a mixture with said pearlescent pigments.

In a preferred embodiment the coating comprises one or more binderpolymers and/or waxes, in a mixture with said pearlescent pigments andwith magnetic or diamagnetic metallic pigments.

In a preferred embodiment the metallic pigments are of various colours,particle sizes and shapes.

In a preferred embodiment the metallic effect pigments of the coatingare those normally used for exterior grade paint.

Therefore the coating contains pearlescent pigments and can optionallycontain metallic pigments as well as the pearlescent pigments.

Furthermore, the coating may also contain organic and inorganic pigmentsin addition to the pearlescent pigments and the metallic pigments.

There may also be organic or inorganic pigments contained in the basesupport which may be coloured.

The invention therefore provides a pearlescent paper material(paper/card) of high lightfastness, thanks to a specially designed pulpand a specific surface coating treatment.

The paper material of the invention also proves to be perfectlyprintable with high printing quality and makes it possible to achieveparticular graphic effects that are difficult to achieve withconventional coated papers.

In detail, the paper material of the invention comprises a base supportmade up of a mixture of cellulosic fibres and it contains at least onepolymeric substance, adapted to give the mixture of fibres mechanicalstrength (when dry or wet), and an inorganic filler, adapted to give thematerial good machinability characteristics.

The base support has at least one surface (face) treated with at leastone surface adhesive to which a coating is applied, so that, due to thecombined effect of the composition of the base support and the surfacetreatment, the paper material has a pearlescent effect with variouscolours. Clearly, both faces of the base support may be treated in thesame way.

Preferably, the polymeric substance included in the base supportcomprises one or more colophony-based and/or alkyl-ketene-dimer-basedand/or acetylsuccinic-acid-based and/or epochlorohydrin-based resins,and/or modified starches; and the inorganic filler is a mineral fillercomprising one or more substances selected from the group constituted bycarbonates, kaolins, talc and mixtures thereof.

The surface adhesive is for example an adhesive based on starch and/orpolyvinyl alcohol- and/or acrylic-, polyurethane- and/orstyrene-butadiene-based polymers. As mentioned, the paper materialaccording to the invention is provided with a coating, applied on thetreated surface and clearly, the paper material may have both surfacestreated and provided with a coating.

In particular, the coating is formed by one or more binder polymers(e.g. polyurethane- and/or silicone-, and/or acrylic-,styrene-butadiene-, polyvinyl acetate-, polyvinyl alcohol-based polymersand the like) and/or waxes, in a mixture with dyes and pigments, e.g.pearlescent pigments of various colours, particle sizes and shapes withthe characteristic of being stable to the exposure of the UV componentof sunlight.

The quantity of polymer per face is preferably comprised between 5% byweight and 100% by weight with respect to the pigments; the paper basisweight of the paper material is comprised between about 90 and about 450g/m²; the quantity of coating spread onto each face is comprised betweenabout 5 and about 20 g/m².

The coating may be coloured and/or spread onto a coloured base support;preferably, coloured pastes and organic or inorganic pigments are used.

In accordance with a further aspect of the present invention, the papermaterial described hereinabove is realized using the following method.

The base support is realized first, using a substantially knownpaper-forming technique, for example on a continuous machine formanufacturing paper.

In essence, an aqueous pulp comprising a mixture of cellulose fibres andcontaining the polymeric substance (colophony-based and/oralkyl-ketene-dimer-based and/or acetylsuccinic-acid-based and/orepochlorohydrin-based resins, and/or modified starches) and theinorganic filler (carbonates, kaolins, talc, etcetera) is prepared.

Subsequently, water is removed from the pulp so as to form a basesupport of the paper material.

This is followed by a step of surface treatment of one or both faces ofthe base support with an aqueous solution of surface adhesive, forexample made up of a 10% by weight aqueous solution of starch, and/or 5%by weight of acrylic adhesive, or similar adhesives.

After the surface treatment with adhesive, the method then comprises asmoothing step of the base support, wherein the base support is smoothedup to Bendtsen ISO 2494 roughness values of less than approximately 450ml/min., preferably of less than approximately 400 ml/min. andapproximately around 350 ml/min, followed by an application step of thecoating previously described.

Preferably, the application of the coating takes place by spreading withan air knife or a smoothing blade, roto-offset, rotographic andflexographic techniques.

This is followed by step of drying the coating, carried out in aninfrared and/or hot-air oven at a temperature within the range of 100°C. approximately to 180° C. approximately and with an oven time rangingbetween 0.5 and 4 minutes.

Lastly, the method comprises a step of mechanically treating the surfaceprovided with the coating, particularly a smoothing and/or an embossingstep.

It remains understood that modifications and variants that are notbeyond the scope of the invention as defined in the appended claims, maybe made concerning the paper material and the relative manufacturingmethod disclosed and illustrated herein.

1. A paper material comprising a base support, made up of a mixture ofcellulose fibres comprising at least one polymeric substance, which isadapted to give the mixture of fibres mechanical strength, and aninorganic filler, said base support having at least one coating appliedon said treated surface, wherein said coating comprises at leastpearlescent pigments of high lightfastness.
 2. The paper materialaccording to claim 1, wherein said pearlescent pigments are of variouscolours, particle sizes and shapes.
 3. The paper material according toclaim 1, wherein said coating comprises one or more binder polymers orwaxes, in a mixture with said pearlescent pigments.
 4. The papermaterial according to claim 1, wherein said coating comprises one ormore binder polymers or waxes, in a mixture with said pearlescentpigments and with magnetic or diamagnetic metallic pigments.
 5. Thepaper material according to claim 1, wherein said pearlescent pigmentsare borosilicates or aluminosilicates.
 6. The paper material accordingto claim 5, wherein said pearlescent pigments are transparentborosilicates or aluminosilicates coated with metal oxides.
 7. The papermaterial according to claim 1, wherein the polymeric substance includedin the base support comprises one or more colophony-based,alkyl-ketene-dimer-based, acetylsuccinic-acid-based, orepochlorohydrin-based resins, or modified starches.
 8. The papermaterial according to claim 1, wherein the inorganic filler is a mineralfiller comprising one or more substances selected from the groupconsisting of carbonates, kaolins, talc and mixtures thereof.
 9. Thepaper material according to claim 1, wherein the surface adhesive is anadhesive based on starch, polyvinyl alcohol, acrylic, polyurethane orstyrene-butadiene polymers.
 10. The paper material according to claim 3,wherein the binder polymers comprise at least one of polyurethane-,acrylic-, polyvinyl alcohol-, styrene-butadiene or silicone basedpolymers.
 11. A method for manufacturing a paper material, comprisingthe steps of: preparing an aqueous pulp of cellulose fibres, comprisingat least one polymeric substance adapted to give the fibres mechanicalstrength, and an inorganic filler; removing water from the pulp so as toform a base support of the paper material; treating at least one surfaceof the base support with at least one surface adhesive; performing asmoothing process on the treated surface of the base support; andapplying a coating comprising at least pearlescent pigments of highlightfastness to the smoothed treated surface.
 12. The method accordingto claim 11, wherein the treated surface is smoothed up to Bendsten ISO2494 roughness values of less than approximately 450 ml/min., preferablyof less than approximately 400 ml/min. and approximately around 350ml/min.
 13. The method according to claim 11, wherein the coatingapplied to the treated surface comprises, in a mixture, said pearlescentpigments, magnetic or diamagnetic metallic pigments, and one or morebinder polymers or waxes.
 14. The method according to claim 11, whereinthe step of applying the coating takes place by spreading with an airknife or a smooth blade.
 15. The method according to claim 11, furthercomprising a step of drying the coating, carried out in an infraredand/or hot-air oven at a temperature within the range of 100° C.approximately to 180° C. approximately and with an oven time rangingbetween 0.5 and 4 minutes.
 16. The method according to claim 15,wherein, after drying the coating, a step of mechanically treating thesurface provided with the coating is performed, particularly a smoothingstep or an embossing step.